Phase Separation And Reactive Compatibilization Of Polymer Blend

Phase separation and reactive compatibilization are among the mostfrequently used methods to control phase morphology and mechanicalproperties of polymer blends, which attracts considerable attention overthese years. In this thesis, many characterization techniques such asrotational rheometer, Scanning and Transmission Electron Microscopy(SEM, TEM) were applied to investigate the effect of nanosilica on phasebehavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile)(PMMA/SAN) blends, phase separation kinetics of PMMA/SAN,reactive compatibilization of Polystyrene/poly(ethylene--octene)(PS/POE) and PS/PMMA interfacial coupling reaction. The results are asfollows:1. Surface initiated Atom Transfer Radical Polymerization (ATRP)was successfully applied to graft polystyrene chains to the surface ofnanosilica. The selective distribution of nanosilica either in PMMAmatrix or at the interfaces between PMMA and SAN was achievedthrough varying chain length of PS grafts. And then, both optical andrheological methods were adopted to investigate the effect of nanosilica on the phase behavior of PMMA/SAN blend. It was found that theparticle and its location had significant influence on the rheologicaltransition temperature but little impact on optically determined binodaltemperature (cloud temperature). This discrepancy was discussed throughmorphology observation via TEM for blends under different phaseseparation conditions. It was found that nanosilica suppressed coarseningof morphology during phase separation. The most striking slowdown wasfound in off-critical blends with nanoparticles located at the interfaces.On the other hand, nanoparticles preferentially locating in the minorphase could act as nucleation sites but decreased the total number ofnuclei at the same time. The difference in the rheological transitiontemperatures is ascribed to the effect of nanoparticles on the components’viscoelasticity and the morphology evolution during phase separation.2. Phase separation kinetics of PMMA/SAN blends was monitoredby the rheometer through dynamic time sweep and cycle frequency sweep.It was found that in near-critical polymer blend, such as PMMA/SAN70/30, blends’ moduli in higher frequencies increased with increasingseparation time. And this increase was attributed to the composition’svariation in phase domains. Thus, the evolution of domains’ compositionswas calculated based on the increasing storage moduli at higherfrequencies. And those equilibrium values of domains’ compositions wereconsistent with that from binodal phase diagram. 3. The reaction compatibilization of PS/POE blends was investigatedvia combination of rheometer and SEM. It was found that the interfacialcopolymer density was much lower than saturation value even we assumeall of the reactive formed copolymer stayed at the interfaces. In otherwords, the reaction brought fewer reduction in interfacial tension. Evenso, those copolymer still brought significant compatibilization effect tothe reactive polymer blend, stabilizing the phase morphology duringannealing. Thus, we can reach a conclusion that the compatibilizationeffect of copolymer was realized mainly via suppressing droplet coalesce.4. ATRP method was successfully applied to synthesize endfunctional polymers with low polydispersity index, PS-NH2andPMMA-Anhy-Anth. Moreover, after introducing anthracene into PMMAchains, the quantitive characterization of interfacial coupling reactionbetween PS and PMMA under low concentration was realized viacoupling GPC with UV detector.